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Plotting gain and phase when simulating amplifier

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STOIKOV

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is is typical to plot gain and phase when simulating an amplifier. What does "phase" mean for you ?
 

Gain and phase

phase is the output delay of the overall system. So if you have a phase compensation in a control system you design your system transfer function as your requirements. In some time if your system needs some matching then you design the transfer function as zero phase that is impedance is real. in this case at this frequency your system is no phase delayed and may be RF output...

there are many examples...
 

    STOIKOV

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Re: Gain and phase

You need to plot both phase and gain for the amplifier. You will notice that both of them will stop being linearly dependent on the input at some point. (this does not happen simultaneously)

Basically it tells you where the non linearity or the compression is beginning

hope this helps
 

    STOIKOV

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Re: Gain and phase

STOIKOV,
Phase is important in analysing the closed loop response of the amplifier. If the phase lag is 180 deg or more at the frequency at which the open loop gain goes to zero, the circuit will be unstable. The close the phase lag is to 180 degrees at this frequency,m the more oscillatory the step response will be. The term linearity must not be confused with phase linearity. Linearity simply means that superposition can be applied. Phase linearity means that the phase is directly proportional (linear) with trespect to frequency. Phase linearity is not necessary for circuit linearity.
Regards,
Kral
 

    STOIKOV

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Re: Gain and phase

for any amplifier we need the o/p magnitude to be linear with i/p..
for that purpose only we make some assumptions while using MOS as an amplifier...
1more thing is we want the amp gain to b constant at all frequencies..so that we can made to operate it at desired freq w/o any performance degradation..
now coming to phase ...its indication of delay b/n i/p and o/p....if reactive elements r high accordingly it will vary.
phase linearity means phase s proportional to freq.
 

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